The Characteristic polynomial of the matrix A is (Taking 'R' as roots symbol - lamda)

R^3 + 20*R^2 - 41*R = 0

Thus by taking a R as common, R( R^2 + 20*R - 41) = 0

Hence, clearly the minimum Eigen value is 0

A shortcut for this kind of problems, if you find the constant term as 0 in the characteristic poly., then definitelyone of the eigen value is 0 and obviously that would be minimum.Char. PolyR^3 - R^2(sum of diagonal elements) + R(sum of minors of diagonal elements) - (determinant(A)) = 0(or)R^3 - R^2(sum of eigen values) + R(sum of eigen value pair product) - (product of eigen values) = 0